Polymorphisms of Fc gamma-receptors RIIa, RIIIa, and RIIIb in patients with adult periodontal diseases

Polymorphisms influencing the binding affinity between the Fcgamma receptors and IgG of different subclasses are thought to be of importance in the individual susceptibility to infections with Gram-negative bacteria contributing to periodontal disease. One hundred and fifty-four Caucasian subjects were clinically and radiographically examined for their periodontal status and genotyped for their allelic pattern of FcgammaRIIa, FcgammaRIIIa, and FcgammaIIIb polymorphism. In assessing periodontitis according to mean probing depth and attachment loss, no differences were found in allele frequencies or combined allotypes between the subjects with mild or moderate and those with severe signs of periodontitis. However, the extent and severity of bone loss were significantly associated with the genotype of the receptor FcgammaRIIIa. An increased risk of severe bone destruction was observed in individuals carrying the FcgammaRIIIa-VV genotype (OR = 5.3; 95% CI 1.4-26.2). FcgammaRIIIb is in linkage disequilibrium with FcgammaRIIIa. Hence it is also related to periodontal disease. There is no indication of an association between the polymorphism of FcgammaRIIa and periodontitis. The results are evidence that the FcgammaRIIIa genotype coding for the high affinity receptor imposes an additional risk of bone loss as does the FcgammaRIIIb genotype coding for the low affinity receptor.

Perioperative management of a patient with Fechtner syndrome

Fechtner syndrome is a rare type of familial thrombocytopenia associated with large platelets, leukocyte inclusions, and features of Alport's syndrome. The bleeding tendency is usually mild, but severe hemorrhages have been reported. This is the case of a patient with Fechtner syndrome who was scheduled to undergo tonsillectomy. The patient had a history of easy bruising in childhood and a markedly prolonged bleeding time. Administration of DDAVP led to normalization of the bleeding time, and the patient underwent surgery without complications. With this approach the use of platelet concentrates could be avoided.

Glucosamine sulfate does not crossreact with the antibodies of patients with heparin-induced thrombocytopenia

OBJECTIVE

To assess the crossreactivity of glucosamine sulfate, used for treatment of degenerative joint disease with antibodies induced in heparin-induced thrombocytopenia (HIT).

BACKGROUND

HIT is a severe adverse effect of heparin therapy induced by an immunological mechanism. The antibodies in HIT are induced by a complex of heparin and, in most cases, platelet factor 4. Hereby generation of the antigen is not strictly dependent on heparin. Heparin can be substituted by a variety of polysulfated carbohydrates. In vitro and in vivo crossreactivity of HIT antibodies has been demonstrated for a chemically polysulfated chondroitin-like substance (Arteparon, Luitpoldwerke, Munich, Germany), formerly used for chondroprotection. Another drug widely used in the treatment of degenerative joint disease is glucosamine sulfate. Glucosamine is a building block of glycosaminoglycans, of which heparin is the clinically most important. Many patients with degenerative joint disease use glucosamine sulfate. This group is also at the highest risk to develop HIT following joint replacement surgery.

METHODS

We examined the interactions of glucosamine sulfate (DONA 200-S, Opfermann, Wiehl, Germany) with platelets and antibodies of patients with HIT in and without the presence of heparin. Sera of 5 HIT patients and platelets of 4 healthy donors were used. The binding of HIT antibodies to PF4/glucosamine sulfate complexes was assessed by an ELISA.

RESULTS

HIT antibodies did not activate platelets in the presence of glucosamine sulfate in a serotonin-release assay. Preincubation with glucosamine sulfate did not inhibit platelet activation by HIT antibodies in the presence of heparin (0.2 IU/ml). Antibodies bonded to PF4/heparin but not to PF4/glucosamine sulfate complexes.

CONCLUSIONS

In contrast to sulfated glycosaminoglycans, there is no evidence for an immunological crossreactivity of HIT antibodies between heparin and glucosamine sulfate.

A comparison of danaparoid and lepirudin in heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is a hypercoagulable syndrome strongly associated with thrombosis that is usually treated with drugs that inhibit factor Xa (danaparoid) or thrombin (lepirudin). In the present study the outcome of HIT-patients treated with danaparoid or lepirudin was compared using the single or combined endpoints of new thromboembolic complications (new TECs), amputations and/or death, and major bleeding. HIT-patients treated with lepirudin were enrolled in two prospective trials and patients, who were identified in the same two laboratories during the same time period, who were not enrolled into these studies but treated with danaparoid, were assessed retrospectively according to a standardized questionnaire. 126 danaparoid (60.3% female) and 175 lepirudin treated patients (58.3% female) fulfilled the same inclusion and exclusion criteria. In a time-to-event-analysis the cumulative risk of combined endpoint was higher in HIT-patients without thromboembolic complication at baseline treated with danaparoid (usually in prophylactic dose 750 anti-factor Xa units b.i.d. or t.i.d.s.c.) as compared to lepirudin (aPTT adjusted) (P = 0.020). Whereas HIT-patients with TEC at baseline who were usually treated with therapeutic dose had a similar outcome in both treatment groups (P = 0.913). Major bleeding occurred in 2.5% (95% CI 0.5-7.0%) of danaparoid treated patients as compared to 10.4% (95% CI 6.3-15.9%) of lepirudin treated patients until day 42 (P = 0.009). This indicates that the efficacies of therapeutic doses of danaparoid or lepirudin in preventing death, amputation or new TEC in HIT-patients do not differ largely, but the risk of bleeding seems to be higher in lepirudin treated patients. The prophylactic dose of danaparoid approved in the European Union for HIT without TEC at baseline seems suboptimal. A prospective comparative trial is required to verify these preliminary conclusions.

Recombinant hirudin in clinical practice: focus on lepirudin

Clinical applications for recombinant hirudins have been investigated for the past 10 years. The first indication for which a hirudin-lepirudin-has been approved is treatment of heparin-induced thrombocytopenia (HIT). Also, the recently completed trials for use of lepirudin in unstable angina indicate a potentially new indication. This review describes pharmacology and clinical applications of lepirudin with an emphasis on HIT and unstable angina. An overview of usage of lepirudin in acute coronary syndromes is given, as well as a summary of rare indications for lepirudin, such as extracorporeal circulation, for which comprehensive data are lacking.

Emergency cardiopulmonary bypass in a bilaterally nephrectomized patient with a history of heparin-induced thrombocytopenia: successful reexposure to heparin

We present a case of emergency coronary artery bypass surgery in a bilaterally nephrectomized patient with a history of heparin-induced thrombocytopenia. The patient was reexposed short term to heparin during cardiopulmonary bypass and did not develop any complications related to heparin-induced thrombocytopenia. Despite intraoperative neutralization of heparin severe bleeding complications occurred, probably resulting from preoperative therapeutic anticoagulation with rhirudin in conjunction with an increased half-life of more than 2 days.

Autosomal-dominant giant platelet syndromes: a hint of the same genetic defect as in Fechtner syndrome owing to a similar genetic linkage to chromosome 22q11-13

Families with 3 different syndromes characterized by autosomal dominant inheritance of low platelet count and giant platelets were studied. Fechtner syndrome is an autosomal-dominant variant of Alport syndrome manifested by nephritis, sensorineural hearing loss, and cataract formation in addition to macrothrombocytopenia and polymorphonuclear inclusion bodies. Sebastian platelet syndrome is an autosomal-dominant macrothrombocytopenia combined with neutrophil inclusions that differ from those found in May-Hegglin syndrome or Chediak-Higashi syndrome or the Dohle bodies described in patients with sepsis. These inclusions are, however, similar to those described in Fechtner syndrome. Other features of Alport syndrome, though, including deafness, cataracts, and nephritis, are absent in Sebastian platelet syndrome. Epstein syndrome is characterized by macrothrombocytopenia without neutrophil inclusions, in addition to the classical Alport manifestations-deafness, cataracts, and nephritis-and it is also inherited in an autosomal-dominant mode. We mapped the disease-causing gene to the long arm of chromosome 22 in an Italian family with Fechtner syndrome, 2 German families with the Sebastian platelet syndrome, and an American family with the Epstein syndrome. Four markers on chromosome 22q yielded an LOD score greater than 2.76. A maximal 2-point LOD score of 3.41 was obtained with the marker D22S683 at a recombination fraction of 0.00. Recombination analysis placed the disease-causing gene in a 3.37-Mb interval between the markers D22S284 and D22S693. The disease-causing gene interval in these 3 syndromes is similar to the interval described recently in an Israeli family with a slightly different Fechtner syndrome than the one described here. Recombination analysis of these 3 syndromes refines the interval containing the disease-causing gene from 5.5 Mb to 3.37 Mb. The clinical likeness and the similar interval containing the disease-causing gene suggest that the 3 different syndromes may arise from a similar genetic defect.

Very low platelet counts in post-transfusion purpura falsely diagnosed as heparin-induced thrombocytopenia. Report of four cases and review of literature

Differential diagnosis between post-transfusion purpura (PTP) and heparin-induced thrombocytopenia (HIT) can be difficult in the initial stages of thrombocytopenia, as the early clinical presentations are often similar. Four patients are described who were suspected clinically of suffering from HIT. All four patients had recent blood transfusions and platelet alloantibodies, thus the diagnosis of PTP was made. One lethal gastrointestinal and one retroperitoneal hemorrhage developed in two of the four patients. Unusually, one patient was male and two different platelet alloantibodies were present in his serum; in another patient platelet alloantibodies and HIT-antibodies were detectable. To arrive at the right diagnosis as quickly as possible is vitally important since treatment, which has to be initiated promptly, is very different for the two syndromes. Thus, we suggest that in patients where HIT is suspected, additional information should be sought. If features consistent with PTP (such as a recent blood transfusion or a marked drop in platelet count to below 15 Gpt/L) are present, we recommend parallel testing for platelet alloantibodies to rule out PTP.

Antihirudin antibodies in patients with heparin-induced thrombocytopenia treated with lepirudin: incidence, effects on aPTT, and clinical relevance

Hirudin, a potent and specific thrombin inhibitor, is a protein of nonhuman origin and therefore potentially immunogenic. The primary objectives of this investigation were to determine the incidence of antihirudin antibodies (ahir-ab) in patients with heparin-induced thrombocytopenia (HIT) who received lepirudin as parenteral anticoagulation and to determine the incidence of death, limb amputation, new thromboembolic complications (TECs), and major hemorrhage in patients who had ahir-ab, compared with patients who were ahir-ab negative. The investigation used data from 2 prospective multicenter studies with the same study protocol, in which HIT patients received 1 of 4 intravenous lepirudin dosage regimens. The treatment duration was 2 to 10 days. Ahir-ab were determined by a newly developed enzyme-linked immunosorbent assay (ELISA). Eighty-seven of 196 evaluable patients (44.4%) had ahir-ab of the IgG class. Development of ahir-ab was dependent on the duration of treatment (ahir-ab-positive patients 18.6 days vs ahir-ab-negative patients 11.8 days; P =.0001). Fewer ahir-ab-positive than ahir-ab-negative patients died (P =.001). Ahir-ab did not cause an increase in limb amputation (P =.765), new TECs (P >.99), or major bleedings (P =.549). In 23 of 51 (45.1%) evaluable patients in whom ahir-ab developed during treatment with lepirudin ( = 12% of all lepirudin treated patients), the ahir-ab enhanced the anticoagulatory effect of lepirudin. Ahir-ab are frequent in patients treated with lepirudin for more than 5 days. Ahir-ab are the first example for a drug-induced immune response causing enhanced activity of a drug. Therefore, during prolonged treatment with lepirudin, anticoagulatory activity should be monitored daily to avoid bleeding complications.

Heparin-induced thrombocytopenia with thromboembolic complications: meta-analysis of 2 prospective trials to assess the value of parenteral treatment with lepirudin and its therapeutic aPTT range

This meta-analysis focuses on 2 prospective studies in patients with heparin-induced thrombocytopenia (HIT) and thromboembolic complication (TEC) who were treated with lepirudin (n = 113). Data were compared with those of a historical control group (n = 91). The primary endpoint (combined incidence of death, new TEC, and limb amputation) occurred in 25 lepirudin-treated patients (22.1%; 95% CI, 14.5%-29.8%): 11 died (9.7%; 95% CI, 4.9%-16.8%), 7 underwent limb amputation (6.2%; 95% CI, 2.5%-12.3%), and 12 experienced new TEC (10.6%; 95% CI, 5.8%-18.3%). The risk was highest in the period between diagnosis of HIT and the start of lepirudin therapy (combined event rate per patient day 6.1%). It markedly decreased to 1.3% during lepirudin treatment and to 0.7% in the posttreatment period. From the start of lepirudin therapy to the end of follow-up, lepirudin-treated patients had consistently lower incidences of the combined endpoint than the historical control group (P =.004, log-rank test), primarily because of a reduced risk for new TEC (P =. 005). Thrombin-antithrombin levels in the pretreatment period (median, 43.9 microg/L) decreased after the initiation of lepirudin (at 24 hours +/- 6 hours; median, 9.18 microg/L.) During treatment with lepirudin, aPTT ratios of 1.5 to 2.5 produced optimal clinical efficacy with a moderate risk for bleeding, aPTT ratios lower than 1. 5 were subtherapeutic, and aPTT levels greater than 2.5 were associated with high bleeding risk. Bleeding events requiring transfusion were significantly more frequent in patients taking lepirudin than in historical control patients (P =.02). In conclusion, this meta-analysis provides further evidence that lepirudin is an effective and acceptably safe treatment for patients with HIT.

Neurologic complications in immune-mediated heparin-induced thrombocytopenia

OBJECTIVE

To evaluate neurologic complications in patients with immune-mediated heparin-induced thrombocytopenia (HIT) with respect to incidence, clinical characteristics, outcome, and therapy.

METHODS

One hundred and twenty consecutive patients with immune-mediated HIT were recruited over a period of 11 years and studied retrospectively for the occurrence of neurologic complications. Diagnosis of HIT was based on established clinical criteria and confirmed by detection of heparin-induced antibodies using functional and immunologic tests.

RESULTS

Eleven of the 120 patients (9.2%) presented with neurologic complications; 7 suffered from ischemic cerebrovascular events, 3 from cerebral venous thrombosis, and 1 had a transient confusional state during high-dose heparin administration. Primary intracerebral hemorrhage was not observed. The relative mortality was much higher (Chi-square test, p < 0.01) in HIT patients with neurologic complications (55%) as compared to patients without neurologic complications (11%). The mean platelet count nadir in neurologic patients was 38 +/- 25 x 10(9)/l on average, and was lower in patients with fatal outcome compared to those who survived (21 +/- 13 x 10(9)/l versus 58 +/- 21 x 10(9)/l; p < 0.05, Wilcoxon test). In three patients neurologic complications preceded thrombocytopenia. There was a high coincidence of HIT-associated neurologic complications with other HIT-associated arterial or venous thrombotic manifestations.

CONCLUSION

Neurologic complications in HIT are relatively rare, but associated with a high comorbidity and mortality. HIT-associated neurologic complications include cerebrovascular ischemia and cerebral venous thrombosis. They may occur at a normal platelet count.

Heparin-induced thrombocytopenia in paediatric patients--a review of the literature and a new case treated with danaparoid sodium

The immunological form of heparin-induced thrombocytopenia (HIT) is a potentially life-threatening adverse reaction of heparin medication. It is mediated by multimolecular complexes consisting of platelet factor 4 (PF4)-heparin-IgG which bind to platelets via platelet Fc gamma receptors. Cross-linking of multiple Fc gamma receptors results in platelet activation, platelet aggregation and enhanced thrombin generation with a increasing risk of developing new thrombosis. In children, data on HIT are sparse. This review of the literature reports on 8 children aged 3 months to 15 years and 14 newborns suffering from HIT. Additionally, we report one new case treated with danaparoid sodium. Thrombotic complications were venous (n = 12) and arterial (n = 15). The children received heparin either for a spontaneous thrombotic event, for severe cardiac diseases or to maintain patency of intravascular catheters which are used for nutrition, blood sampling, and for application of medication. After diagnosis of HIT they were further anticoagulated with aspirin, warfarin, danaparoid sodium, lepirudin or low molecular weight heparin.

CONCLUSION

Although HIT is less frequently reported in newborns and children, paediatricians should be aware of HIT in childhood as a potential complication of heparin application. The widespread practice of flushing catheters with heparin should also be debated in view of the risk of triggering the primary immune-response of HIT. In 1999, treatment options for further parenteral anticoagulation of HIT patients are danaparoid sodium (a low-molecular weight heparinoid) and lepirudin (a direct thrombin inhibitor).

Heparin-induced thrombocytopenia--pathogenesis and treatment

Heparin-induced thrombocytopenia (HIT) is now recognized as the most frequent immune-mediated adverse drug reaction. During the last decade, fundamental aspects of the pathogenesis of HIT have been resolved. The understanding of some the mechanisms underlying the development of new, paradox thromboembolic complications in HIT led to the concept that thrombin generation plays a key-role in clinically manifest HIT. Consequently new therapeutic concepts imply the use of drugs with either indirect or direct anti-thrombin activity such as donaparoid-sodium and the recombinant hirudin lepirudin. During the last years results of first prospective studies assessing various treatment regimens in HIT became available. Although data of randomized trials are still missing some treatment recommendations can already be drawn from these studies. This review summarizes key aspects of the pathogenesis of HIT and provides an overview of current treatment strategies.

Lepirudin (recombinant hirudin) for parenteral anticoagulation in patients with heparin-induced thrombocytopenia. Heparin-Associated Thrombocytopenia Study (HAT) investigators

BACKGROUND

We prospectively investigated lepirudin for further parenteral anticoagulation in patients with heparin-induced thrombocytopenia (HIT).

METHODS AND RESULTS

Patients with confirmed HIT (n=112) received lepirudin according to need for 2 to 10 days (longer if necessary): A1, treatment: 0.4 mg/kg IV bolus, followed by 0.15 mg. kg(-1). h(-1) intravenous infusion, n=65; A2, treatment in conjunction with thrombolysis: 0.2 mg/kg, followed by 0.10 mg. kg(-1). h(-1), n=4; and B, prophylaxis: 0.10 mg. kg(-1). h(-1), n=43. Outcomes from 95 eligible lepirudin-treated patients were compared with those of historical control patients (n=120). Complete laboratory response (activated partial thromboplastin time ratio >1.5 with </=2 dose increases and platelet count normalization by day 10) was achieved in 65 lepirudin-treated patients (69.1%; 95% CI, 59. 3% to 78.3%). At 2 weeks after cessation of lepirudin, 11 patients died (9.8%), 10 underwent limb amputation (8.9%), and 20 suffered a new thromboembolic complication (17.9%). The average combined event rate per patient-day decreased from 5.1% in the pretreatment period to 1.5% in the treatment period. Thirty-five days after HIT confirmation, fewer lepirudin-treated patients than historical control patients had experienced >/=1 outcome (cumulative incidence 30.9% versus 52.1%; relative risk [RR] 0.71; P=0.12, log-rank test). Bleeding events were more frequent in the lepirudin group than the historical control group (cumulative incidence at 35 days, 44.6% versus 27.2%; RR 2.57; P=0.0001, log-rank test). No difference was observed in bleeding events requiring transfusion (cumulative incidence at 35 days, 12.9% versus 9.1%; RR 1.66; P=0.23, log-rank test); no intracranial bleeding was observed in the lepirudin group.

CONCLUSIONS

Lepirudin effectively prevents death, limb amputations, and new thromboembolic complications and has an acceptable safety profile in HIT patients. Treatment should be initiated as soon as possible if HIT is suspected.

The alpha2 gene coding sequence T807/A873 of the platelet collagen receptor integrin alpha2beta1 might be a genetic risk factor for the development of stroke in younger patients

The polymorphisms C807T and G873A of the platelet integrin alpha2beta1 (collagen receptor glycoprotein [GP] Ia-IIa) are linked to the expression density of this receptor. The GPIa T807/A873 allele causes a higher receptor expression, enhancing platelet binding to collagen. This might present a genetic predisposition for the development of thromboembolic complications. In this case-control study, the genotypes of the GPIa C807T polymorphism and presence of conventional risk factors (hypertension, diabetes mellitus, and smoking) were compared in stroke patients and patients without cerebrovascular disease (non-CVD patients) </=50 years of age (n = 45 and 41, respectively) and in stroke patients and non-CVD patients more than 50 years of age (n = 182 and 129, respectively. In patients </=50 years of age, the T807 allele was the only overrepresented variable (P =.023; odds ratio, 3.02; 95% confidence interval, 1.20 to 7.61) and an independent risk factor, whereas the presence of conventional risk factors was similar between stroke patients </=50 years of age and non-CVD patients </=50 years of age. Large epidemiological studies should prove whether the platelet collagen receptor GPIa-IIa T807 allele is an independent risk factor for the development of stroke in younger patients.

Successful thrombolysis of right atrial and ventricle thrombi encircling a temporary pacemaker lead in a patient with heparin-induced thrombocytopenia type II

Only few reports exist addressing the problem of temporary pacemaker leads associated with thromboembolic disease. We report the case of a 67-year-old patient who required a temporary transfemoral pacemaker due to AV block grade III. The patient developed extensive right atrial and ventricle thrombus formation attached to the pacing wire, as well as venous thrombosis at the insertion site due to heparin-induced thrombocytopenia type II (HIT type II). After short-term thrombolysis with 1 mg rt-PA/kg b.w. complete resolution of all clots could be shown by B-mode sonography and transthoracic, as well as transesophageal echocardiography.

First workshop for detection of heparin-induced antibodies: validation of the heparin-induced platelet-activation test (HIPA) in comparison with a PF4/heparin ELISA

BACKGROUND

No data exist regarding the inter-laboratory reproducibility of the heparin-induced-platelet-activation (HIPA) test, the most widely used functional assay in Germany for the detection of heparin-induced thrombocytopenia (HIT) antibodies.

METHODS

Nine laboratories used an identical protocol to test eight different sera with the HIPA test. Five laboratories also tested the sera with a platelet factor 4 (PF4)/heparin-complex ELISA. Cross-reactivity with danaparoid-sodium was assessed using 0.2 aFXa units instead of heparin in the HIPA test.

RESULTS

Two of nine laboratories had no discrepant HIPA test results. Four laboratories differed in one sample, one reported two discrepant results, and two laboratories reported more than two discrepant results. Cross-reactivity with danaparoid-sodium test results differed among laboratories. PF4/heparin ELISA results were identical in all five laboratories.

CONCLUSION

The HIPA test requires strict quality control measures. Using both a sensitive functional assay (HIPA test) and a PF4/heparin ELISA will allow detection of antibodies directed to antigens other than PF4/heparin complexes as well as detection of IgM and IgA antibodies with PF4/heparin specificity.

[The feasibility of preoperative autologous blood donation in children]

According to the experience to date, autologous blood donation is feasible in children and is not accompanied by an increased risk as compared to adult patients. If indicated, autologous blood donation should therefore be offered to pediatric patients using the same criteria as in adults. Problems specific to blood donation in children may arise from limited compliance of the children. In addition, the amount of the blood drawn and the amount of the anticoagulant has to be adjusted according to the weight of the child. This may present difficulties especially in smaller facilities, since there are no blood donation systems available to date that specifically suit the pediatric patient. The necessary manipulations to adjust the blood donation system to the weight of the child might enhance the risk of bacterial contamination.

Recombinant hirudin (lepirudin) provides safe and effective anticoagulation in patients with heparin-induced thrombocytopenia: a prospective study

BACKGROUND

The immunological type of heparin-induced thrombocytopenia (HIT) is the most frequent drug-induced thrombocytopenia. This study evaluated the efficacy of recombinant hirudin (r-hirudin or lepirudin), a potent thrombin inhibitor, for anticoagulation in patients with confirmed HIT.

METHODS AND RESULTS

Eighty-two patients in this prospective, multicenter study received 1 of 4 intravenous r-hirudin regimens: A1, HIT patients with thrombosis (n=51), 0.4-mg/kg bolus and then 0.15 mg. kg-1. h-1; A2, HIT patients with thrombosis receiving thrombolysis (n=5), 0. 2-mg/kg bolus and then 0.1 mg. kg-1. h-1; B, HIT patients without thrombosis (n=18), 0.1 mg. kg-1. h-1; and C, during cardiopulmonary bypass surgery (n=8), 0.25-mg/kg bolus and then 5-mg boluses as needed. Response criteria were increase in platelet count by >/=30% to >10(9)/L and activated partial thromboplastin time (aPTT) values 1.5 to 3.0 times baseline values achieved with a maximum of 2 dose increases. No placebo control was used for ethical reasons. Outcomes of a subset of r-hirudin-treated patients who met predefined inclusion criteria (n=71) were compared with those of a historical control group (n=120) for combined and individual incidences of death, amputations, new thromboembolic complications, and incidences of bleeding. Platelet counts increased rapidly in 88.7% of r-hirudin-treated patients with acute HIT. In regimens A1 and A2, the 25% and 75% quartiles of the aPTT were within the target range at all but 1 time point. The incidence of the combined end point (death, amputation, new thromboembolic complications) was significantly reduced in r-hirudin patients compared with historical control patients (P=0.014). During first selected treatment, the adjusted hazard ratio for r-hirudin patients versus historical control was 0.279 (95% CI, 0.112 to 0.699; P=0.003). Bleeding rates were similar in both groups.

CONCLUSIONS

r-Hirudin treatment is associated with a rapid and sustained recovery of platelet counts, sufficient aPTT prolongations, and true clinical benefits for patients with HIT.

Rekombinantes Hirudin zur weiteren Antikoagulation bei Patienten mit Heparin-induzierter Thrombozytopenie

Hirudin ist ein spezifischer Thrombininhibitor, der unabhängig von Kofaktoren wie Antithrombin und Heparin-Kofaktor II wirkt. Im Gegensatz zu Heparin wird r-Hirudin durch PF4 nicht inaktiviert. Hirudin bewirkt auch eine Hemmung von Thrombus-gebundenem Thrombin und von an Fibrinabbauprodukte gebundenem Thrombin, das vor einer Hemmung durch Heparin geschützt ist. Bei der Heparin-induzierten Thrombozytopenie (HIT) führt eine verstärkte Iη-vivo-Thrombozyten-aktivierung zur Freisetzung großer Mengen von PF4 und zur exzessiven Thrombinbildung. Betroffene Patienten müssen weiter parenteral antikoaguliert werden. Zur Beurteilung des klinischen Potentials von Hirudin bei dieser Indikation führten wir zwei prospektive Multizenterstudien mit 82 und 112 Patienten durch. In diesen Studien ermöglichte das Hirudin Lepirudin eine effektive parenterale Antikoagulation von HIT-Patienten. Durch Lepirudin kann die Inzidenz schwerwiegender Folgen der HIT reduziert werden. Blutungskomplikationen und die Induktion von Anti-Hirudin-Antikörper sind die wichtigsten unerwünschten Wirkungen der Therapie mit Hirudin.

Heparin-induced thrombocytopenia: new insights into the impact of the FcgammaRIIa-R-H131 polymorphism

Heparin-induced thrombocytopenia (HIT), a severe complication of heparin treatment, can be associated with new thrombotic complications. HIT antibodies activate platelets via the platelet Fcgamma-receptor (FcgammaRIIa), which carries a functionally relevant polymorphism (FcgammaRIIa-R-H131). The effect of this polymorphism on the clinical manifestations of HIT is controversial. We determined prospectively the FcgammaRIIa-R-H131 genotypes in 389 HIT patients, in 351 patients with thrombocytopenia or thrombosis due to causes other than HIT and without detectable HIT antibodies, and in 256 healthy blood donors. For this purpose, a novel nested sequence-specific primer-polymerase chain reaction (SSP-PCR) was developed. FcgammaRIIa-R/R131 was found to be overrepresented in the HIT patients (27%) compared with the control groups (non-HIT patients [21%] and blood donors [20%]). In a subgroup of 122 well-characterized HIT patients, the genotype distribution in patients presenting with thrombocytopenia only was compared with that of patients who developed thromboembolic complications. The frequency of FcgammaRIIa-R/R131 among patients with thrombotic events was significantly elevated (37% v 17%; P = .036). Our results indicate that genotype distribution can be correlated to the clinical outcome of patients with HIT. We speculate that the reduced clearance of immune complexes in patients with the FcgammaRIIa-R/R131 allotype causes prolonged activation of endothelial cells and platelets, thus increasing the risk for thrombotic complications.

Heparin-induced thrombocytopenia: pathophysiology and clinical concerns

Heparin-induced thrombocytopenia (HIT) is a severe immunological adverse effect of heparin treatment. Recently the pathogenesis of HIT has been resolved regarding the mechanisms of platelet activation, the nature of the most important antigens and the involvement of the clotting cascade. HIT seems to be associated with massive generation of thrombin, which contributes to the thromboembolic complications. Based on these findings, treatment of patients with acute HIT should include cessation of all heparins and further treatment with an anticoagulant with antithrombin activity. Currently, the two most important compounds for further anticoagulation of HIT-patients are danaparoid-sodium and recombinant hirudin.

Release of mediators of systemic inflammatory response syndrome in the course of a severe delayed hemolytic transfusion reaction caused by anti-D

BACKGROUND

In vitro studies suggest that mediators of systemic inflammatory response syndrome are generated in the course of hemolytic transfusion reactions. Evidence for the in vivo significance of these findings is given by the present clinical and laboratory analysis of a severe delayed hemolytic transfusion reaction (DHTR).

CASE REPORT

A 67-year-old patient (blood group O, D-negative) with a negative pretransfusion antibody screen received a massive transfusion because of arterial bleeding (Day 1). The transfusion of group O, D-positive red cell concentrates was unavoidable because of limited supplies. At Day 10, the patient developed a DHTR with symptoms of septic-toxic syndrome and signs of hemolysis; he received an exchange transfusion. Serologic markers, as well as proinflammatory and anti-inflammatory mediators, were monitored at the onset of the DHTR and during the exchange transfusion.

RESULTS

At Day 10, the direct antiglobulin test was positive; anti-D was present, most likely as the result of an anamnestic immune response. Interleukin (IL)-1 was not detectable; all other mediators monitored were elevated: IL-1 receptor antagonist, tumor necrosis factor, IL-6, IL-8, IL-10, neopterin, elastase, C3a-desArg, C-reactive protein, and fibrinogen. Most of the values declined during the exchange transfusion, which was followed by an improvement of the clinical presentation.

CONCLUSIONS

Mediators of systemic inflammatory response syndrome were released in the course of a DHTR caused by anti-D. Severe clinical symptoms could be treated successfully by exchange transfusion.

Atypical heparin-induced thrombocytopenia complicated by intracardiac thrombus, effectively treated with ultra-low-dose rt-PA lysis and recombinant hirudin (Lepirudin)

A serious retroperitoneal bleeding occurred in a 56-year-old male patient receiving unfractionated heparin due to multiple pulmonary embolism. After reducing the heparin dose, the patient developed a new pulmonary embolism and a large thrombus in the right atrium. Concomitantly, the platelet count dropped to a value of 29 g/l. Heparin-induced thrombocytopenia (HIT) was confirmed by a functional assay, the heparin-induced platelet activation (HIPA) assay, whereas the results of a platelet factor 4/heparin complex ELISA were repeatedly negative. This indicated that the patient's HIT antibodies were directed towards an antigen other than platelet factor 4/heparin complexes. For treatment of the atrial thrombus, an ultra-low-dose lysis with rt-PA (2 mg/h, intravenously) was administered for a period of 52 h, overlapping with systemic treatment with recombinant hirudin (Lepirudin, Refludan, 0.06-0.14 mg/kg/h intravenously). The aim was to enhance lysis of the thrombus without increasing the haematoma, and at the same time keep the risk of fulminant pulmonary embolism due to thrombus fragmentation as low as possible. The cardiac thrombus disappeared within 48 h, without new signs of pulmonary embolism. Platelet counts normalized within nine days.

[Fc receptor-dependent platelet activation results independently of glycoprotein complex IIb/IIIa]

Platelets of a patient with Glanzmann's thrombasthenia revealed the same activation pattern when stimulated with antibodies of patients with heparin-associated thrombocytopenia (HAT) or immune complexes. This was investigated by the 14C-serotonin release test and by changes in phosphorylation of p20 and p47. Platelet activation by HAT antibodies was completely inhibited by a moab against the platelet FcRII (IV. 3) and by Fc fragments of human IgG but not by F(ab)2 fragments. We conclude that platelet activation via the FcRII occurs independently of the glycoprotein complex IIb/IIIa. Therapeutical approaches targeting GP IIb/IIIa-fibrinogen interaction seem to be not appropriate in HAT.

[Suppression of FcRII by intravenously administerd IgG is dependent of preparation procedures of immunoglobulins]

The effect of different i.v. IgG preparations on FcRII-dependent platelet activation by antibodies from patients with heparin-associated thrombocytopenia (HAT) was investigated. Only one preparation (treated with pH 4 and traces of pepsin) sufficiently inhibited FcRII-dependent platelet activation (20 mg/ml). We conclude that administration of high-dose i.v. IgG is efficient for acute treatment of HAT, dependent on the manufacturing process.

Adenosine diphosphate (ADP) and ADP receptor play a major role in platelet activation/aggregation induced by sera from heparin-induced thrombocytopenia patients

The molecular basis for heparin-induced thrombocytopenia (HIT), a relatively common complication of heparin therapy, is not yet fully understood. We found that pretreatment of platelets with AR-C66096 (formerly FPL 66096), a specific platelet adenosine diphosphate (ADP) receptor antagonist, at a concentration of 100 to 200 nmol/L that blocked ADP-dependent platelet aggregation, resulted in complete loss of platelet aggregation responses to HIT sera. AR-C66096 also totally inhibited HIT serum-induced dense granule release, as judged by measurement of adenosine triphosphate (ATP) release. Apyrase, added to platelets at a concentration that had only minor effects on thrombin- or arachidonic acid-induced aggregation, also blocked completely HIT serum-induced platelet aggregation. Furthermore, AR-C66096 inhibited platelet aggregation and ATP release induced by cross-linking Fc gamma RIIA with specific antibodies. These data show that released ADP and the platelet ADP receptor play a pivotal role in HIT serum-induced platelet activation/aggregation. The thromboxane receptor inhibitor, Daltroban, had no effect on HIT serum-induced platelet activation whereas GPIIb-IIIa antagonists blocked platelet aggregation but had only a moderate effect on HIT serum-induced dense granule release. Pretreatment of platelets with chondroitinases but not with heparinases resulted in concentration dependent inhibition of HIT serum-induced platelet aggregation. These novel data relating to the mechanism of platelet activation induced by HIT sera suggest that the possibility should be examined that ADP receptor antagonists or compounds that inhibit ADP release may be effective as therapeutic agents for the prevention or treatment of complications associated with heparin therapy.

[Prevention of thromboembolism as a cause of thromboembolic complications. A study of the incidence of heparin-induced thrombocytopenia type II]

PROBLEM

A life-threatening complication of the thrombembolism prophylaxis with heparin is heparin-induced thrombocytopenia (HIT) type II. HIT type II is based on immunological mechanisms. Even low, subcutaneously applied doses may produce HIT type II. In those patients, continued application may cause thromboembolic complications. The most important symptom of HIT type II is a decrease of platelets.

METHODS

In a prospective study, we investigated the incidence of HIT type II within the period from 01.07.95 to 30.06.96 in orthopedic patients. We also evaluated the importance of the daily platelet count from the fifth postoperative day for the early diagnosis of HIT type II and a possible reduction of the thrombosis rate. The study included 307 patients after primary implantation of hip and knee endoprosthesis and after hip endoprosthesis replacement. All patients received 3 x 5000 IU/d of unfractionated heparin subcutaneously. Whenever there was a decrease of platelets of at least 50% in relation to the preoperative value or whenever thrombembolic complications occurred, serum was analyzed by the heparin-induced platelet activation test (HIPA).

RESULTS

20 patients developed HIT type II. This corresponds to an incidence of 6.5%. 10 of the HIT type II antibody positive patients (50%) developed thrombembolic complications. 3 patients (0.9%) of the group studied developed clinically symptomatic thrombembolic complications without evidence of heparin antibodies. The total risk of getting thrombembolic complications was 4.2% (13 patients). 3.3% (10 patients) of the entire group developed HIT type II antibody associated thrombembolic complications; 1 patient died. The lethality in the HIT type II antibody positive patient group amounted to 5%. The patients with HIT type II received LMW heparinoid Orgaran (AKZO-Organon, The Netherlands) or hirudin (as a clinical trial). The comparison group (retrospective study from 17.10.92 to 16.10.93) was composed of 262 patients with the same operations and equal thromboembolism prophylaxis. The platelet count was made only as part of routine diagnostic tests. 21 patients (8.0%) developed clinically symptomatic thrombembolic complications. The difference in the thrombosis rate between these two groups of patients is statistically significant. Unrecognized HIT type II is probably the reason for the high thrombembolic complication rate in the comparison group.

CONCLUSIONS

The daily platelet count from the fifth postoperative day and from the first day in case of reexposure to heparin is an important measure for the early diagnosis of HIT type II.

Polymorphisms of the human platelet antigens HPA-1, HPA-2, HPA-3, and HPA-5 on the platelet receptors for fibrinogen (GPIIb/IIIa), von Willebrand factor (GPIb/IX), and collagen (GPIa/IIa) are not correlated with an increased risk for stroke

BACKGROUND AND PURPOSE

A recent study has described a high incidence of the human platelet antigen (HPA)-1b alloantigen in patients with myocardial infarction. We investigated the distribution of gene polymorphisms of platelet glycoproteins (GPs) in patients with cerebrovascular disease (CVD) and stroke. The polymorphic systems we have studied are HPA-1 and HPA-3 on the fibrinogen receptor (GPIIb/IIIa), HPA-2 on the von Willebrand factor receptor (GPIb/IX), and HPA-5 on one of the platelet collagen receptors (GPIa/IIa).

METHODS

DNA was isolated from peripheral blood collected from 218 consecutive stroke patients, 165 neurological inpatients without signs of CVD, and 321 healthy blood donors. The genotypes of HPA-1, HPA-2, HPA-3, and HPA-5 were determined by sequence specific primer polymerase chain reactions.

RESULTS

The calculated allele frequencies were as follows: for CVD patients, HPA-1a/b 0.81/0.19, HPA-2a/b 0.91/0.09, HPA-3a/b 0.61/0.39, and HPA-5a/b 0.92/0.08; for inpatient HPA-1a/b 0.83/0.17, HPA-2a/b 0.91/0.09, HPA-3a/b 0.62/0.3 and HPA-5a/b 0.93/0.07; and for blood donors, HPA-1a 0.85/0.15, HPA-2a/b 0.94/0.06, HPA-3a/b 0.60/0.40, and HPA 5a/b 0.92/0.08. There were no statistically significant difference for the analyzed HPA polymorphism frequencies either between the CVD patients and the non-CVD inpatients or the CVD patients and blood donors. However, the HPA-1b genotype was slightly more frequent in patients (CVD and non-CVD) than in the healthy blood donors.

CONCLUSIONS

Our results indicate that the HPA-1, HPA-2, HPA-3, and HPA-5 polymorphisms are not associated with an increased risk for stroke.

Monitoring of r-hirudin anticoagulation during cardiopulmonary bypass--assessment of the whole blood ecarin clotting time

The use of recombinant (r) hirudin as an anticoagulant in performing extracorporeal circulation systems including cardiopulmonary bypass (CPB) devices requires a specific and easy to handle monitoring system. The usefulness of the celite-induced activated clotting time (ACT) and the activated partial thromboplastin time (APTT) for r-hirudin monitoring has been tested on ex vivo blood samples obtained from eight patients treated with r-hirudin during open heart surgery. The very poor relationship between the prolongation of the ACT and APTT values and the concentration of r-hirudin as measured using a chromogenic factor IIa assay indicates that both assays are not suitable to monitor r-hirudin anticoagulation. As an alternative approach a whole blood clotting assay based on the prothrombin-activating snake venom ecarin has been tested. In vitro experiments using r-hirudin-spiked whole blood samples showed a linear relationship between the concentration of hirudin added and the prolongation of the clotting times up to a concentration of r-hirudin of 4.0 micrograms/ml. Interassay coefficients (CV) of variation between 2.1% and 5.4% demonstrate the accuracy of the ecarin clotting time (ECT) assay. Differences in the interindividual responsiveness to r-hirudin were analyzed on r-hirudin-spiked blood samples obtained from 50 healthy blood donors. CV-values between 1.8% and 6% measured at r-hirudin concentrations between 0.5 and 4 micrograms/ml indicate remarkably slight differences in r-hirudin responsiveness. ECT assay results of the ex vivo blood samples linearily correlate (r = 0.79) to the concentration of r-hirudin. Moreover, assay results were not influenced by treatment with aprotinin or heparin. These findings together with the short measuring time with less than 120 seconds warrant the whole blood ECT to be a suitable assay for monitoring of r-hirudin anticoagulation in cardiac surgery.

Decreased platelet membrane anisotropy in patients with adrenoleukodystrophy treated with erucic acid (22:1)-rich triglycerides

Low platelet count and bleeding diathesis have been observed in patients with adrenoleukodystrophy (ALD) treated with erucic acid (22:1)-rich triglycerides ("Lorenzo's oil'). To investigate possible alterations of biophysical membrane properties, we measured platelet membrane anisotropy, which is inversely related to membrane fluidity, in 16 patients with and in 3 patients without treatment. In patients on treatment, platelet membrane anisotropy was significantly decreased. Additionally, we found increased platelet concentrations of 22:1 and compromised in vitro platelet aggregation response. The decrease of platelet membrane anisotropy is probably a main cause of bleeding diathesis. Long-term haematological side-effects must be considered in ALD patients treated with Lorenzo's oil.